Light emitting diode (LED) lighting fixtures are becoming increasingly popular due to their advantages over lighting fixtures that employ other lighting technologies such as fluorescent and incandescent bulbs. LED lighting fixtures excel in energy consumption efficiency, reliability, and length of lifetime compared to fluorescent and incandescent technologies. Additional advantages of LED lighting fixtures, when compared specifically to fluorescent lighting fixtures, include the ability to turn on instantly. Moreover, the lifetime of an LED lighting fixture is unaffected by cycling on and off, such as when powered on and off during normal usage.
LED fixtures often include a plurality of individual LED elements mounted on a substrate, with the combined output of the individual LED elements providing a desired brightness and/or color of light. One issue relating to such lighting fixtures is that when one or more of the individual LED elements fail, unwanted changes can occur to the overall brightness and/or color of the light emitted from the fixture. Such changes may or may not be easily observable by the naked eye, making physical inspection difficult.
In view of this, attempts have been made to automatically detect when an individual LED element or a lighting fixture has failed or is failing. In some systems it is common to add circuitry to a device that is providing power to the lighting fixture to measure the power used. In the case of a single lighting fixture, if the power/current is zero, it can be assumed that the lighting fixture has failed. In the case where the device is powering multiple lighting fixtures, if the power/current is observed to drop significantly it can be inferred that at least one lighting fixture has failed.
In the case of LEDs, failure typically results in the loss of light intensity (including complete failure in which no light is emitted), but with continued current draw. For this reason, failure detection techniques that employ power monitoring are not effective in determining LED failures. Thus, testing and troubleshooting fixtures in an LED lighting control network can be time consuming, often involving a significant amount of manual labor. Commissioning agents often need to identify the fixture(s) in a specific room using building layout documents, and then may need to walk to the room and troubleshoot each lighting fixture in that room. Adding to the complexity is that master (central) controllers used in such systems are often located in electrical closets or behind ceilings, and it may be necessary to connect a user input to the master controller which, in turn, requires accessing and opening the master controller to connect the user input thereto.
In addition to the aforementioned problems, when LED lighting fixtures (or individual LED elements) fail, it can impact daylighting functionality of the associated lighting system. Since daylighting levels for a particular space are often set once (e.g., when the lighting system for a room is initially installed), failure of one or more LED lighting fixtures in a room can adversely affect lighting levels in the room throughout the day.
In view of these deficiencies in current systems, it would be desirable to provide a system and method for monitoring one or more LED lighting fixtures to automatically determine when intensity changes occur so that replacement or repair can be performed quickly and efficiently. In addition, it would be desirable for such a system and method to identify the individual LED lighting fixture that is affected so that a maintenance operations can be directed to the specific fixture, eliminating the need for room walk-throughs. Further, it would be desirable for the system and method to automatically adjust daylighting levels when an LED lighting failure is detected, and to readjust daylighting levels once the affected LED lighting fixture is repaired.